1. Field of the Invention
This invention relates to pulse generating means which are mounted on utility meters such as water meters and gas meters. The meters drive the pulse generator which produces an electrical pulse for a given volume of flow through the meter which pulse is transmitted by means of an electrical connection or other known transmission means to a pulse counter located remote from the meter, usually on the exterior wall of the residence to facilitate meter reading without access to the interior of the residence where the meter is located.
2. Background of the Invention and Description of the Prior Art
The present invention is an improvement to the pulse generating means shown in U.S. Pat. No. 3,685,353 to Gestler et al dated Aug. 22, 1972. In that patent a pulse generator is disclosed comprised of a gear train which is coupled to the flow responsive element of the water meter by means of a magnetic coupling. As the flow responsive element moves under the influence of the flow of water through the meter, the gear train within the pulse generator is driven, which in turn rotates a coil against the bias of a spring. After the coil has rotated approximately 1800.degree. the coil is disengaged from the drive train and allowed to rapidly return to its initial position under the force of the spring. The rapid return of the coil to its initial position causes the turns of the coil to cut lines of force produced by a permanent magnet which causes a momentary voltage to be generated in the turns of the coil in a manner manner well known in the art. This voltage pulse is then transmitted to a pulse counter which is usually located remote from the meter.
In that patent the release mechanism is comprised of a camming vane driven by a gear train which in turn is driven by the flow responsive element of the meter. The camming vane is mounted for rotation about an axis which is offset from the axis of rotation of the rotatable coil. The camming vane engages a drive pin on the coil and as the camming vane rotates, because of the offset relationship between the axis of rotation of the vane and the coil, the pin moves radially outward on the camming vane until it is disengaged from the camming vane at its radially outermost point. The coil is then disengaged from the drive train and allowed to rapidly return to its initial position under the bias of the spring.
As the pin and coil are driven by the vane about the axis of the coil, the return spring on the coil causes the pin to exert an increasing force against the vane and the rest of the register drive train. As the pin moves radially outward away from the axis of the vane, the resisting torque applied to the vane by the spring is also increased by increase in the lever arm at which the force of the spring is applied to the vane. Therefore the back load or resisting torque which the rotatable coil imposes on the drive train is increased not only by the increase in spring force as the coil is rotated against the bias of the spring, but also by the increase in the lever arm at which the biasing force of the spring is applied to the drive train. This non-uniform backload has a range of maximum and minimum values which require that the strength of the magnetic coupling between the flow responsive element of the meter and the register drive, as well as other elements in the drive train be designed for maximum backload. Obviously if the backload could be made more uniform design of the drive train and magnetic coupling would be greatly simplified.